The use and construction of balloon catheters is well known in the medical art, as described for example in U.S. Pat. No. Re. 32,983 (Levy) and U.S. Pat. No. 4,820,349 (Saab). Balloon catheters are typically utilized as dilatation devices for dilating a blood vessel, e.g. a coronary artery, or other body cavity, although other uses have been developed, e.g., temporarily anchoring an instrument within a body lumen so that a surgical or therapeutic procedure can be performed. Other patents generally showing the application of various types of balloon catheters include U.S. Pat. No. 4,540,404 (Wolvek), U.S. Pat. No. 4,422,447 (Schiff), and U.S. Pat. No. 4,681,092 (Cho et al.).
It is also well known in the medical art to employ catheters having shafts formed with a plurality of lumens in instances where it is necessary or desirable to access the distal end of the catheter or a particular internal body location simultaneously through two or more physically separate passageways. For example, U.S. Pat. No. 4,576,772 (Carpenter) is directed to increasing the flexibility or articulatability of a catheter having a shaft formed with a plurality of lumens that provide distinct conduits for articulating wires, glass fiber bundles, irrigation, and vacuum means.
It is also known, as shown in U.S. Pat. No. 4,299,226 (Banka) and U.S. Pat. No. 4,869,263 (Segal et al.), to employ multi-lumen catheters with a balloon. The Banka patent shows a double-lumen catheter shaft of coaxial construction wherein the outer lumen carries saline solution to inflate a balloon, and an inner lumen, located coaxially inside the outer lumen, is adapted to receive a stylet or guide wire. In the Banka patent, the double-lumen dilatation catheter is designed to be coaxially contained within the single lumen of a larger diameter guide catheter.
The Segal et al. patent shows a more complex dilatation catheter having five separate, non-coaxial lumens (FIGS. 1 and 2) extending through the catheter shaft, including a balloon inflation lumen 18, a distal lumen 17, a wire lumen 22, a pulmonary artery lumen 26, and a right ventricular lumen 28. Lumens 17 and 18 extend the entire length of the catheter shaft from the proximal extremity to the distal extremity. Lumen 17 exits through the distal extremity 14b of the catheter shaft. The distal extremity of lumen 18 is in communication with the interior of balloon 16 to permit inflation and deflation. Lumens 22, 26 and 28, on the other hand, only pass partly or completely through the larger diameter, proximal portion 14a of the catheter shaft. A transducer 21 mounted at the transition between portions 14a and 14b is coupled to circuitry by wires 24 extending through wire lumen 22. Proximal portion 14a is stated to have a diameter of, for example, 0.098 inches whereas distal portion 14b has a diameter, for example, of 0.060 inches. The Segal et al. catheters are prepared by extrusion (col. 2, lines 53-54).
In the above-cited prior art, it should be appreciated that the term "multi-lumen" in the phrase "multi-lumen balloon catheters" means that the catheter shaft is multi-lumen (as opposed to the balloon secured to the shaft). In accordance with the present invention, it is the balloon itself that is multi-lumen. It is believed that there are many applications where an inflatable balloon having multiple, distinct channels or lumens that are formed as a part of the inflatable balloon would be very desirable. As used herein, the terms "balloon" and "balloon lumen" therefore mean a thermoplastic tubular segment having the properties of being very thin-walled (less than 0.0015 inches thick), high strength, flexible, readily inflatable under a predetermined range of fluid pressures, and readily collapsible under vacuum. It is also typical for such balloons to have at least one tapered end, although according to the present invention it is not necessary. For high strength, these balloons are normally expanded and oriented in at least one direction and preferably in two directions, i.e. biaxial orientation. Orientation occurs when a thermoplastic material is expanded or stretched under certain conditions with the result that the material has a much greater strength than before expansion. Such balloons, and methods of preparing them, are described in U.S. Pat. No. 4,820,349 (Saab), U.S. Pat. No. Re. 32,983 (Levy), and European Patent Specification No. 0274411 (Saab), which are incorporated herein by reference. For some applications, a balloon segment having the general properties described above can be affixed to an elongated, relatively thick-walled (0.002 inches or thicker) catheter shaft. For other applications, the elongated, thin, side walls of the balloon can serve as the catheter shaft when the balloon is inflated.
The multi-lumen balloons of the present invention are distinguished from the multi-lumen balloon catheters of the prior art, as discussed above, in that the walls defining the lumens are formed as an integral part of the balloon. As used herein, the terms "integral part" and "integrally formed" each mean that each lumen of the multi-lumen balloon shares a common wall portion with part of at least one balloon lumen. By contrast, the prior art shows lumens that are integrally formed as a part of a conventional catheter shaft and are defined by relatively thick walls of that shaft (e.g. Segal et al.), catheter lumens that communicate with or terminate in a balloon segment (e.g. Banka and Segal et al.), and lumens in a shaft that passes coaxially through a balloon segment (e.g. Banka). The relatively thick walls that define the lumens of conventional multi-lumen catheter shafts typically range from about 0.002-0.010 inches in wall thickness and, in any event, are not high tensile strength or readily inflatable under fluid pressure, nor are they readily collapsible under vacuum when operating at the pressures for which the device is designed. Most balloon catheter shafts are made by extrusion of a thermoplastic material. The resulting shafts are typically not substantially oriented, therefore not high tensile strength. Such balloon catheter shafts are not inflatable as balloons at pressures at which the balloons typically operate, for the obvious reason that the shafts are supposed to remain stiff, and not inflate or deflate. Thus, the multi-lumen catheters of the prior art cannot, by themselves, function as balloons. As a result the design of multi-lumen catheters which use balloons has been limited because these features provide design constraints.
For example, a perfusion catheter utilizes a balloon to perform an angioplasty procedure to dilate coronary arteries which are partially closed due to arterio-sclerosis. While this procedure is often effective in relieving the symptoms caused by the disease by dilating the blood vessels for a substantial length of time, it will be evident that the balloon itself will occlude the blood vessel while it is inflated within the vessel. Accordingly, perfusion catheters are equipped with at least one additional lumen extending through the catheter shaft. The shaft is provided with openings that communicate with this additional lumen on opposite sides of the balloon (the sides of the shaft both distal and proximate from the balloon) so that blood will flow though the lumen when the balloon is inflated reducing the risks to the patient. However, the shaft is typically of a small cross-sectional diameter, with the perfusion lumen being even smaller so that blood flow is still substantially reduced.
These and other limitations of the prior art catheters are overcome with the multi-lumen balloons of this invention.